Fix release publish failure by normalizing nested artifact paths

[Copilot]

Publish GitHub release failed because release assets downloaded by actions/download-artifact were stored in nested directories, while the normalization step only searched the artifact root. As a result, required assets (e.g., .deb) were not discovered and release creation aborted.

• Root cause addressed: recursive asset discovery

  • Updated release asset normalization to search the full artifact tree instead of only top-level files.
  • This aligns with the actual structure produced by merged artifact downloads (deb/, rpm/, appimage/, binary/, etc.).

• Release contract preserved

  • Existing strict checks remain: exactly one asset is required per expected pattern.
  • Output naming remains unchanged (SCADmate_<version>_<os>_<arch>...) so downstream release expectations stay stable.

• Relevant change

  # before
  find "$asset_dir" -maxdepth 1 -type f -name "$pattern" -print0
  
  # after
  find "$asset_dir" -type f -name "$pattern" -print0